Allergy is a major and growing health concern around the world. As societies become more affluent and reduce the incidence of contagious disease, the prevalence of allergic disease increases. Finding effective treatments for allergy, both preventive and therapeutic, is a growing challenge for today's healthcare industry. Traditionally, management of allergy has concentrated on alleviation of symptoms, using antihistamines and medications which relieve allergic symptoms including nasal congestion, dermatitis and asthma, such as decongestants, creams, anti-inflammatories and bronchodilators. Allergen avoidance is another strategy for allergy management, but this is often difficult or impossible, particularly in the case of pervasive allergens such as pollen. A third alternative is specific allergy vaccination, in which patients are inoculated with the allergen causing the allergy in order to obtain an improvement in the patient's immune status. This kind of treatment has the advantage of altering the course of the illness to prevent the manifestation of symptoms, rather than simply alleviating symptoms.
Injective immunotherapy (subcutaneous immunotherapy or SCIT) was first reported in 1911 and has been used in clinical practice since the 1970s. However, the invasive nature of the therapy, requiring regular clinician visits, and problems with side effects—including, in rare cases, anaphylaxis and death—have prevented it from being a routinely used treatment of allergy. Immunotherapy via administration of allergen to mucosa, such as the oral mucosa of the mouth and gut, has also been explored. Sublingual immunotherapy (SLIT), in which the vaccine is administered underneath the tongue and absorbed via the sublingual mucosa, is a well-established alternative to injective immunotherapy. SLIT has been shown to be comparable to SCIT in terms of efficacy and has a superior safety profile. It is now generally preferred to SCIT due to the less invasive nature to the technique and the lower risk of side effects, as the occurrence of harmful side effects from SLIT is relatively low. However, the expense of the treatment is still a major factor in slowing down the uptake of SLIT. Identifying methods of pre-selecting patients likely to respond well to the therapy is thus of interest, as is the identification of methods of tracking patient response to therapy.